My 2-channels mains are more than capable of getting me evicted..and they are shelf speakers.
bass response in an 11x14 room is enough that a subwoofer is not needed, at all. I actually rattled the windows and shook the floor when it was in my home theater, watching lord of the rings, return of the king.. the dream of Gandalf's fight with the Balrog...there is a deep rumble in that track. Without a sub, I managed to shake the place that violently at moderate volumes. With a sub....well those speakers almost overpowered a 120w 8" yamaha subwoofer, I could just barely tell it was even on.
Point is....My setup can do this with less than 40w rms. the speakers in question are 6 1/2" kit speakers.
If you have a small room, you don't need tons of wattage.
Now in a loft, with a high ceiling, you may want some more power, but I wouldn't reccoemnd going overboard anyways. A decent speaker sounds just as good at low power as it will at higher power ranges...so long as you don't underpower the speaker.